This invention relates to a novel seasoning liquor and a method for producing the same.
In the production of soy sauce in the conventional art, soybean and wheat are used as nitrogen sources. That is, after the heat treatment of the mixture of soybean and wheat, the treated mixture is inoculated with koji-mold (seed culture for the preparation of koji) and it is then incubated to obtain koji (mold preparation containing developed mycelium of koji-mold used for preparing soy source, alcoholic liquor, etc.). The fermentable mash is prepared by adding a saline solution to the koji. In the fermentation of the koji, the protein and starch of koji-substrate are decomposed, respectively, by protease and amylase contained in the koji, and further, lactic acid bacteria and yeast in the koji also act on the mash, thereby obtaining fermented mash for the preparation of soy sauce.
This method is, however, economically disadvantageous in that several months are necessary for the production. In addition, the coefficient of utilization of protein and starch in the used soybean and wheat for soy sauce, is quite low.
Meanwhile, the development of a method for producing seasoning liquors by using corn in place of the above-mentioned soybean and wheat has been desired since the corn can be produced in large quantities at low cost. In other words, corn protein is widely used mainly for the production of animal feed and the rate of production of corn is quite large and stable as compared with those of soy bean and wheat. So that the corn is very abundant as a protein source and inexpensive with the relative price of about 50% of soybean and about 80% of wheat. The amino acid composition in the protein of corn is quite similar to those of soybean and wheat so that the development of production method for seasoning liquor by using corn as the main fermenting material, has been sought. However, any satisfactory method has not been found since the protein of corn is hardly decomposed or digested by enzyme.
Meanwhile, by using soybean and wheat as protein sources, the method for preparing amino acid seasoning liquor by acid decomposition is employed, in which corn is also used in combination. For example, protein is hydrolyzed into amino acids by treating it with a mineral acid such as hydrochloric acid at an elevated temperature. The decomposed product is then neutralized and refined to obtain an amino acid seasoning liquor. In another method, the amino-bonds of protein are partially cut by hydrochloric acid and the product is subjected to fermentation by adding soy sauce mash or draft soy sauce, thereby obtaining a new-type soy sauce. In these methods, the rate of decomposition or utilization can be improved as compared with the conventional fermenting method and the period for production is much reduced, however, the methods are accompanied with the formation of unwanted substances such as levulinic acid and formic acid because the carbohydrates mixed in vegetable protein are easily hydrolyzed as compared with the protein itself and the carbohydrates are decomposed to excess.
In order to eliminate the above-described defects present in the conventional methods and to develop a novel method for producing seasoning liquor of excellent quality by enzymatic digestion of corn protein, the inventors of this invention have carried out extensive studies, and as the result, the present invention has been accomplished.